【作者】 鲍晓宇；

【导师】 施克仁；

【作者基本信息】 清华大学 ， 材料加工工程， 2003， 博士

【摘要】 超声相控阵技术通过对超声阵列换能器中各阵元进行相位控制，获得灵活可控的合成波束。它具有能进行动态聚焦、可进行成像检测、可检测复杂形状物体、能提高检测灵敏度、分辨力和信噪比的多项优点，近年来正成为国际无损检测界的研究热点。本文独创性地设计实现了一个16通道相控阵超声检测实验系统，并在此基础上深入研究了超声相控阵的多项关键技术。在概述了超声检测尤其是超声成像检测的发展历史和现状后，本文说明了相控阵超声检测的优越性，继而详细阐述了相控阵超声检测系统中各项关键技术的原理及其实现方法。本文详细阐述了作者所独立研制的16通道相控阵超声检测实验系统，包括数字化超声发射/接收波束形成、超声信号的低噪声程控放大、多通道高速高精度数据采集、多通道超声信号高速实时处理、基于PCI总线的高速数据传输等全部电路模块的结构及工作原理，并说明了所编写的底层软件系统的框架。本文对超声相控阵系统中各通道发射/接收的相干条件进行了详细的误差分析，阐明了本系统采用的时钟和同步方案，以及改进相控阵时钟精度的方法。对于相位延时这一关键技术，本文着重阐述了以波形激励为基础的数字波形相位延时的原理和实现，经实验达到了很高的发射延时分辨率。对于相控接收延时，本文阐述了一种将延时时钟和采样时钟分离的方案，有效地提高了接收延时分辨率。 对大容量相控采样数据的及时处理是系统的难点之一。本文研究了基于DSP+FPGA的信号处理体系结构，实现了对超声信号的高速实时处理。FPGA实现的数字滤波算法起到了明显的噪声抑制效果，其速度比软件实现大大提高。本文还研究并实现了FPGA的在系统重构，将它的性能优势充分发挥出来。最后本文对所研制的相控阵超声检测系统进行了实验验证。实验表明本系统的相位控制取得了良好的效果，实测聚焦接收信号达到理想值的91％以上。更多还原

【Abstract】 Ultrasonic phased array technique can help to achieve flexible, controllable synthesized ultrasound beam by exciting each element of an ultrasonic array transducer with independent phase delay. Phased array ultrasonic testing can accomplish dynamic focusing, obtain visual image, inspect component of complex geometry. Also it can improve detection sensitivity, resolution and SNR, so it has recently been highly recognized in NDT research domain. In this thesis, a 16-channel experimental phased array ultrasonic testing system is originally designed and developed, upon which several key technologies are thoroughly studied.In this thesis, firstly the history and current situation of ultrasonic testing especially the ultrasonic imaging is outlined. After that the merits of phased array ultrasonic testing are discussed, then the principles and realizations of several key technologies of phased array ultrasonic testing system are explicated in details.In the following chapters, a 16-channel experimental phased array ultrasonic testing system is thoroughly explained, including digital beam forming, low noise programmable amplification of received ultrasound signal, multi-channel hi-speed hi-precision data acquisition, hi-speed real-time processing of multi-channel ultrasound signal, and hi-speed data transfer based on PCI bus. In addition, the frame of software system is built.As concerning to the interference condition between different transmit/receive channels in the system, a detailed error analysis is given, and the clock and synchronization scheme is explicated. The measure adopted to enhance phase clock’s precision is explained. Concerning the key technology of phase delay, the principles and its implementation of digital waveform phase delay based on waveform excitation is explained, which has achieved high transmission phase resolution in experimentation. As to phased array receiving, a scheme of separating the delay clock and sampling clock is explicated, which effectively enhance the phased receiving delay resolution.<WP=8>How to process the large amount of sampling data of ultrasonic phase array system is one of the difficulties in the system. On the basis of the architecture of DSP+FPGA, hi-speed real-time ultrasound signal processing is achieved. Digital filter accomplished in FPGA makes obvious effect on noise suppression, the speed performance is highly improved comparing to software program. In addition, the FPGA’s static reconfiguration and real-time reconfiguration are studied and accomplished, which fully exert the performance advantages of reconfigurable computing.Finally a set of experimentations are done to verify this phased array ultrasonic testing system. The results show that the phase control effect is satisfactory, and the intensity of focused ultrasound beam can reach above 91% of the ideal value.更多还原